For example, in a flat panel type display device such as a liquid crystal display device or an organic EL display device, a display panel constituting the display device has a display region in which a large number of pixels are arrayed in a matrix on a substrate. An active matrix display panel is used broadly as the display panel. In the active matrix display panel, TFT (Thin Film Transistor) devices are provided as switching devices for the pixels arrayed in the display region respectively. Here, a liquid crystal display device will be described as a typical example of such a flat panel type display device.
A display panel constituting an active matrix liquid crystal display device (hereinafter referred to as “liquid crystal panel”) has plane patterns on an opposed surface or opposed surfaces of one or both of a pair of insulating substrates preferably made of glass. A liquid crystal layer is sandwiched between the opposed substrates. TFT devices, pixel electrodes for display, electrodes for applying scanning signals or video signals to the TFT devices, scanning signal lines for transmitting the scanning signals, video signal lines for transmitting the video signals, terminal portions for connecting these signal lines to external drive circuits, etc. are formed on one of the substrates (TFT substrate).
A color filter, a black matrix and an opposed electrode are formed on the other substrate (CF (Color Filter) substrate). There are some available display systems such as a TN (Twisted Nematic) system in which an electric field substantially perpendicular to the liquid crystal sandwiched between the plane patterns of the opposed substrates (also referred to as “vertical electric field”) is applied for display, an IPS (In-Plane Switching) system in which a lateral electric field substantially parallel to the plane patterns is applied for display, etc.
The scanning signal lines, the scanning signal electrodes, the terminal portions for connecting the scanning signal lines with an external drive circuit, the video signal lines, the video signal electrodes, the terminal portions for connecting the video signal lines to an external drive circuit, etc., which are used in the active matrix liquid crystal device, are generally produced as plane patterns by patterning a conductive thin film material such as metal. In the background art, the plane patterns are produced in the following manner. That is, a thin film of metal or the like is formed all over the surface of a substrate in a film forming method such as a sputtering method or a vapor deposition method, and the thin film is processed into a desired shape in a photolithographic process or an etching process.
In addition to the aforementioned background-art technique, there has been proposed a technique for forming plane patterns of wiring or the like in a liquid process using an inkjet apparatus or the like. According to this forming method, the throughput can be improved on a large scale while the cost can be reduced. For example, when wiring patterns are to be formed in a liquid process, ink of a solvent mixed with metal is ejected only to portions where the wiring patterns should be formed. After that, the solvent is evaporated by heat applied thereto, and sintering is performed. Thus, desired wiring patterns can be obtained.
When such a liquid process is used, the photolithographic process and the etching process are dispensable so that the number of processes can be reduced. Since patterns can be formed only in necessary portions due to the liquid process, the cost of materials can be also suppressed so that the cost can be reduced. In addition, the film thickness can be increased without lowering the throughput, so that the resistance of wiring can be lowered easily. Further, since etchant such as acid or alkali to be used in an etching process is dispensable, the load on environment can be also reduced.
As a background-art technique relating to patterning of wiring or the like using an inkjet method which is a typical liquid process technique, JP-A-2000-353594 discloses a film forming technique in which banks are built up on a substrate so as to form grooves in the substrate surface, and the grooves are filled with a thin film material liquid in an inkjet method so as to form a thin film.
According to the inkjet method, a solution including pigment or the like (hereinafter referred to as “ink”) is ejected from nozzles so as to drop onto a substrate to thereby form patterns. The ink is dried or fired to be hardened. Thus, desired patterns can be obtained. Just after the ink lands on the substrate, the ink shows behavior like liquid due to a solvent included therein. When the liquid is dropped onto the substrate, the liquid flows to make its internal pressure constant and reduce its surface area, so that plane patterns are changed. Thus, some kind of pattern is formed into a shape different from a desired shape of the pattern. The fact that the pattern has a shape different from a desired shape means that there occurs an abnormal pattern. For example, liquid may overflow in a tail portion of a pattern, liquid may overflow in a part of a linear pattern, liquid may overflow in a bent portion, or the film thickness may vary due to the shape of a pattern.